gstplayer: implement duration, position, and seek + correctly register an atexit callback to clean all the remaining worker.

kivy/lib/gstplayer/_gstplayer.pyx

@@ -1,4 +1,6 @@
 from libcpp cimport bool
+from weakref import ref
+import atexit
 
 cdef extern from 'gst/gst.h':
     ctypedef void *GstPipeline
@@ -12,6 +14,8 @@ cdef extern from 'gst/gst.h':
     ctypedef unsigned long gulong
     ctypedef void *gpointer
     ctypedef char const_gchar 'const gchar'
+    ctypedef long int gint64
+    ctypedef unsigned long long GstClockTime
 
     ctypedef enum GstState:
         GST_STATE_VOID_PENDING
@@ -20,6 +24,13 @@ cdef extern from 'gst/gst.h':
         GST_STATE_PAUSED
         GST_STATE_PLAYING
 
+    ctypedef enum GstFormat:
+        GST_FORMAT_TIME
+
+    ctypedef enum GstSeekFlags:
+        GST_SEEK_FLAG_KEY_UNIT
+        GST_SEEK_FLAG_FLUSH
+
     ctypedef enum GstStateChangeReturn:
         pass
 
@@ -38,11 +49,21 @@ cdef extern from 'gst/gst.h':
     GstElement *gst_pipeline_new(const_gchar *name)
     void gst_bus_enable_sync_message_emission(GstBus *bus)
     GstBus *gst_pipeline_get_bus(GstPipeline *pipeline)
+    GstStateChangeReturn gst_element_get_state(
+            GstElement *element, GstState *state, GstState *pending,
+            GstClockTime timeout) nogil
     GstStateChangeReturn gst_element_set_state(
             GstElement *element, GstState state) nogil
     void g_signal_emit_by_name(gpointer instance, const_gchar *detailed_signal,
             void *retvalue)
     void g_error_free(GError *error)
+    bool gst_element_query_position(
+            GstElement *element, GstFormat format, gint64 *cur)
+    bool gst_element_query_duration(
+            GstElement *element, GstFormat format, gint64 *cur)
+    bool gst_element_seek_simple(
+            GstElement *element, GstFormat format,
+            GstSeekFlags seek_flags, gint64 seek_pos)
 
 cdef extern from '_gstplayer.h':
     void g_object_set_void(GstElement *element, char *name, void *value)
@@ -54,6 +75,25 @@ cdef extern from '_gstplayer.h':
     void c_appsink_disconnect(GstElement *appsink, gulong handler_id)
 
 
+#
+# prevent gstreamer crash when some player are still working.
+#
+
+cdef list _instances = []
+
+def _on_player_deleted(wk):
+    if wk in _instances:
+        _instances.remove(wk)
+
+@atexit.register
+def gst_exit_clean():
+    for wk in _instances:
+        player = wk()
+        if player:
+            player.stop()
+            player.unload()
+
+
 class GstPlayerException(Exception):
     pass
 
@@ -88,6 +128,7 @@ cdef class GstPlayer:
     cdef GstBus *bus
     cdef object uri, sample_cb
     cdef gulong handler_id
+    cdef object __weakref__
 
     def __cinit__(self, uri, sample_cb):
         self.pipeline = self.playbin = self.appsink = NULL
@@ -98,6 +139,7 @@ cdef class GstPlayer:
         super(GstPlayer, self).__init__()
         self.uri = uri
         self.sample_cb = sample_cb
+        _instances.append(ref(self, _on_player_deleted))
 
         # ensure gstreamer is init
         _gst_init()
@@ -135,7 +177,7 @@ cdef class GstPlayer:
         if self.appsink == NULL:
             raise GstPlayerException('Unable to create an appsink')
 
-        g_object_set_caps(self.appsink, 'video/x-raw,format=RGBA')
+        g_object_set_caps(self.appsink, 'video/x-raw,format=RGB')
         g_object_set_int(self.appsink, 'max-buffers', 5)
         g_object_set_int(self.appsink, 'drop', 1)
         g_object_set_int(self.appsink, 'sync', 1)
@@ -168,12 +210,19 @@ cdef class GstPlayer:
             gst_element_set_state(self.pipeline, GST_STATE_PAUSED)
 
     def unload(self):
+        cdef GstState current_state, pending_state
+
         if self.appsink != NULL and self.handler_id != 0:
             c_appsink_disconnect(self.appsink, self.handler_id)
 
         if self.pipeline != NULL:
+            # the state changes are async. if we want to guarantee that the
+            # state is set to NULL, we need to query it. We also put a 5s
+            # timeout for safety, but normally, nobody should hit it.
             with nogil:
                 gst_element_set_state(self.pipeline, GST_STATE_NULL)
+                gst_element_get_state(self.pipeline, &current_state,
+                        &pending_state, <GstClockTime>5e9)
             gst_object_unref(self.pipeline)
 
         if self.bus != NULL:
@@ -190,7 +239,27 @@ cdef class GstPlayer:
             g_object_set_double(self.playbin, 'volume', volume)
 
     def get_duration(self):
-        return -1
+        cdef gint64 duration = 0
+        if self.playbin == NULL:
+            return -1
+        if not gst_element_query_duration(
+                self.playbin, GST_FORMAT_TIME, &duration):
+            return -1
+        return duration / 1e9
 
     def get_position(self):
-        return -1
+        cdef gint64 position = 0
+        if self.playbin == NULL:
+            return -1
+        if not gst_element_query_position(
+                self.playbin, GST_FORMAT_TIME, &position):
+            return -1
+        return position / 1e9
+
+    def seek(self, percent):
+        if self.playbin == NULL:
+            return
+        seek_t = percent * self.get_duration() * 1e9
+        seek_flags = GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_KEY_UNIT
+        gst_element_seek_simple(self.playbin, GST_FORMAT_TIME,
+                <GstSeekFlags>seek_flags, seek_t)